Vacuum pump

ABSTRACT

A pump rotor ( 11 ) contains a transponder ( 14 ) that can be read out by a reader ( 12 ) of a pump stator ( 10 ). The pump rotor ( 11 ) also contains sensors ( 26 ) for determining operating data (BD), and a memory ( 27 ). The memory ( 27 ) stores either the history of the measured operating data (BD) or a service life characteristic (LDK). In this way, the rate of wear of the respective rotor is determined and stored in the rotor, and the rotor therefore contains all of the information relating to maintenance. The rotor-related information remains in the rotor even if the rotor is used in another vacuum pump.

The invention refers to a vacuum pump with a pump rotor and a pump stator, wherein the pump rotor comprises a transponder having a rotor antenna and the pump stator comprises a reader having a stator antenna and at least one sensor for determining wear-relevant operating data.

WO 2007/025854 A1 (Leybold Vacuum GmbH) describes a vacuum pump wherein the pump rotor carries an electric transducer, such as a temperature sensor, for instance. The pump rotor is provided with a transmitting antenna that transmits data from the transducer to a receiving antenna of the stator. Thereby, exact measured values can be transmitted from the pump rotor to the pump stator.

Vacuum pumps, especially fast rotating turbomolecular pumps rotating at speeds between 10,000 and more than 100,000 rpm, are highly sophisticated devices whose components are subjected to extreme stress due to compression heat, friction heat and centrifugal forces. Excessive rotor temperatures increase the risk of a crash, accelerate material fatigue and change other properties of the pump rotor. The manufacture of a pump rotor and the choice of material for the same have to meet the highest quality standards. Vacuum pumps require regular maintenance during which the pumps are disassembled. This is true in particular for the pump rotor for which a high degree of safety has to be observed. Rotors also have to be cleaned regularly. A pump rotor can be overhauled or maintained at regular time intervals. However, it is more advantageous to set maintenance intervals with consideration to the intensity of operation of the pump rotor. This can be achieved by evaluating measured operating data, such as the temperature or the rotational speed.

The Patent Application DE 10 2007 009 085 A (Oerlikon Leybold Vacuum GmbH) (not pre-published) describes a method for determining the fatigue of a pump rotor of a turbo gas pump, wherein the rotor speed is continuously determined and local speed maxima and minima are determined. The speed maxima and minima are associated to form pairs. A pair fatigue value is calculated for each of the pairs of rotational speed and all pair fatigue values are accumulated to form a total fatigue value. The total fatigue value represents a service life characteristic.

It is an object of the invention to provide a vacuum pump wherein the maintenance management of the pump rotor is independent from the respective pump stator in which the pump rotor is positioned.

The vacuum pump of the invention is defined by the features of claim 1. It is characterized in that the pump rotor comprises a memory that stores operating data or a service life characteristic calculated from the operating data and, upon a request by the reader, reads the same out to the reader via the transponder.

The rotor-side memory contains wear-relevant operating data from the past operation of the pump rotor. Such operating data are, for instance, the temperature, rotational speeds (maxima, minima) or material stresses or expansions. This allows for an evaluation of the intensity of operation with respect to the wear of the material.

A first variant of the invention provides that the measured operating data are stored directly in the rotor-side memory without processing. In a second variant, a service life characteristic is calculated from the operating data, the characteristic depending on the wear and representing the degree of wear of the rotor. Here, wear is to be understood as any kind of abrasion and material fatigue. The service life characteristic is increased by a stress value each time the device is operated, so that an updated service life characteristic is generated. The difference between a respective service life characteristic and a defined limit value gives information about the remaining possible operation time of the pump rotor. When the limit value is reached, the control unit can stop the further operation of the vacuum pump comprising the relevant pump rotor by turning off the drive.

According to the invention the rotor-side memory contains the wear-relevant data of the previous rotor operation so that the pump rotor has a memory of its own. Independent of the vacuum pump into which the pump rotor is placed, it retains the relevant data which it permanently carries with itself. Thus, the pump rotor can give information about its remaining service life or its functionality and its respective degree of wear, independent of the respective pump stator.

In a second variant it is provided that the rotor-side memory stores a service life characteristic calculated from the operating data. Here, the memory capacity can be relatively small since only a characteristic has to be stored. Updating the service life characteristic requires a processor. A processor may be provided at the rotor in combination with the transponder. In this case, the service life characteristic is updated immediately at the pump rotor.

According to another possibility, the operating data and the service life characteristic of the pump rotor are transmitted to a stator-side control unit that forms a stress value from the currently measured operating data and ads the same to the service life characteristic in order to generate an updated service life characteristic. The updated service life characteristic is transmitted to the pump rotor and is stored in the rotor-side memory. In this case, the data are processed on the stator side.

The transponder may be a passive transponder supplied with current by the reader via inductive coupling. However, it may also be an active transponder with a current supply of its own. In any case the transponder preferably includes a memory of its own and, optionally, also a microprocessor. The transponder system is designed for bidirectional information transmission.

According to a preferred embodiment of the invention it is provided that the pump rotor comprises an identity protection memory that stores at least one item of rotor information that can be transmitted to the reader via the transponder, and that the control unit only allows an operation of the vacuum pump if the rotor information meets a predetermined criterion. This makes it possible to guarantee the original character of rotors and their compliance with regulations. The transponder of the pump rotor supplies identity information to the pump stator. The control unit determines whether the pump rotor is an original part and whether it fits with the respective pump stator or is allowed for the same. Thereby, a protection against a confusion of rotors and against the use of non-allowed (copied) rotors in vacuum pumps is achieved. Monitoring the observation of the required degree of safety helps to avoid damages and downtimes.

An embodiment of the invention will be explained in more detail hereunder with reference to the sole FIGURE.

The drawing schematically illustrates the communication system for the transfer of information between the stator and the rotor of a vacuum pump.

The structure of the vacuum pump is the same as in WO 2007/β25854 A1 which is incorporated into the present description by reference thereto. The vacuum pump is a turbomolecular pump with a fast rotating pump rotor. Meshing rows of vanes are situated on the pump rotor and the pump stator. The pump stator 10 and the pump rotor 11 are only schematically illustrated in the drawing, since the primary focus of the invention is on the communication system.

The pump stator includes a reader 12 of an RFID system. The reader is connected with a stator antenna 13. The pump rotor includes a RFID transponder 14 or a tag with a rotor antenna 15. The data transmission between the rotor 12 and the transponder 14 is effected in a wireless bidirectional manner via the antennae 13 and 15.

The reader 12 is provided with a power supply (not illustrated). The power supply of the transponder 14 may be effected wirelessly from the reader via the antennae 13 and 15.

The pump stator 10 includes a memory 16 that communicates bidirectionally with the reader 12. The memory 16 is connected to various sensors 17 that may include a rotational speed sensor, a motor temperature sensor, a housing temperature sensor and a cooling water sensor. A parameter memory 18 contains information about the type of the pump as well as the defined operating values for current, voltage, power and rotational speed.

The memory 16 communicates with a control unit 20 that includes a microprocessor. The control unit 20 controls the motor 21 that drives the pump rotor 11.

The transponder 14 is connected to an identity protection memory 25 that holds rotor information as copy protection data. The rotor information may be a PIN or a TAN.

The pump rotor 11 includes sensors 26 for measuring operating data BD. For instance, these are temperature sensors, strain gauges, acceleration sensors or rotational speed sensors. This enumeration is not exhaustive and other sensor types may be added thereto. The rotor further comprises a rotor-side memory 27 that can also be integrated in the transponder 14.

In one embodiment of the invention the memory 27 is configured such that it stores a history of operating data BD of the pump rotor. In this case a relatively large memory 27 is required.

In another embodiment the memory 27 stores a service life characteristic LDK calculated from the measured operating data BD. In the embodiment illustrated in the drawing, the service life characteristic LDK is recalculated in the stator-side control unit 20. For this purpose, the service life characteristic LDK contained in the memory 27 is transmitted from the transponder 14 to the reader 12 and from there to the control unit 20. In the same manner the current operating data BD are transferred to the control unit 20. From the operating data BD supplied, the control unit 20 calculates a stress value and adds the same to the service life characteristic LDK, e.g. by adding, so as to form an updated service life characteristic LDK_(a). The same is transmitted to the transponder 14 by the reader 12 and is stored in the memory 27 as the current service life characteristic LDK.

The invention guarantees that every pump rotor 11 carries with itself its history or a service life characteristic representing its history. This makes it possible to determine the remaining wear difference until the next maintenance for an individual pump rotor. Thus, a user can determine how much remaining operating time is still available or how many percent of the allowable wear have already occurred. Moreover, it is guaranteed that the control unit 20 prevents the operation of the vacuum pump when the allowable wear limit is reached.

The determination of the service life characteristic is preferably done in accordance with the method described in DE 10 2007 009 085A, the disclosure of which is incorporated into the present description by reference. According thereto, rotational speed maxima and minima of a relevant development of rotational speed over time are determined and are associated in pairs. For each of the rotational speed pairs a pair fatigue value is generated as a stress value. The pair fatigue values are accumulated to a total fatigue value that forms the service life characteristic LDK. 

1. A vacuum pump comprising a pump rotor and a pump stator, the pump rotor including a transponder with a rotor antenna and the pump stator including a reader with a stator antenna and at least one sensor for the detection of wear-relevant operating data, wherein the pump rotor comprises a memory that stores operating data or a service life characteristic calculated on the basis of the operating data and reads the same out to the reader via the transponder.
 2. The vacuum pump of claim 1, wherein a history of operating data of the rotor is stored in the memory of the rotor.
 3. The vacuum pump of claim 1, wherein the operating data and the service life characteristic of the pump rotor are transmitted to a stator-side control unit that forms a stress value from the currently measured operating data and adds this value to the service life characteristic so as to form an updated service life characteristic, and wherein the updated service life characteristic is transmitted to the pump rotor and is stored in the memory of the pump rotor.
 4. The vacuum pump of claim 1, wherein the control unit determines from the history of operating data or the service life characteristic, whether a further operation of the vacuum pump is allowable, and turns off the drive if it is not allowable.
 5. The vacuum pump of claim 1, wherein the pump rotor comprises an identity protection memory that stores at least one item of rotor information that can be transmitted to the reader via the transponder, and wherein the control unit allows an operation of the vacuum pump only if the item of rotor information meets a predetermined criterion.
 6. The vacuum pump of claim 5, wherein the pump rotor comprises a parameter memory which stores at least one item of stator information, and wherein the predetermined criterion is that the item of rotor information and the item of stator information form a previously defined allowable pair of information items.
 7. A method of operating a vacuum pump comprising: rotating a rotor relative to a stator; measuring operating data concerning the rotor; in a memory carried by the rotor, storing at least one of the operating data and a service life characteristic.
 8. The method of claim 7, further including: communicating the operating data from the rotor to the stator via a rotor transponder and a stator transponder; calculating the service life characteristic with a processor associated with the stator transponder; communicating the calculated service life characteristic from the processor to the rotor via the stator transponder and the rotor transponder; and storing the calculated service life characteristic in the memory carried by the rotor.
 9. The method of claim 7, further including: storing rotor information in the memory carried by the rotor; communicating the rotor information via a rotor transponder and a stator transponder to a vacuum pump controller; and allowing of blocking operation of the vacuum pump with the pump controller in accordance with the rotor information.
 10. The method of claim 9, further including: communicating the at least one of the operating data and the service life characteristic from the memory carried by the rotor to the pump controller via the rotor transponder and the stator transponder; controlling operation of the vacuum pump with the pump controller in accordance with the operating data or the service life characteristic. 